1. Field of the Invention
The present invention relates to an electric rotary shaver which causes inner cutters to rotate while contacting substantially disk-form outer cutters, and uses the inner cutters to cut whiskers that are introduced into slits formed in the outer cutters.
2. Description of the Related Art
In electric shavers of this type, shavers that have a plurality of outer cutters are universally known. For example, such shavers include shavers in which two outer cutters are installed side by side in close proximity to each other, and shavers in which three outer cutters are disposed at the vertices of an equilateral triangle. In this structure, in order to improve the shaving characteristics, it is necessary to arrange the outer cutters so that these cutters are depressable and tiltable, thus causing the outer cutters to incline in conformity to the curvature of the shaving surface.
In the shaver disclosed in Japanese Patent No. 2853812, shaving units in which inner cutters are provided in outer cutters are mounted on a retaining plate, and this retaining plate is fastened to the inside wall of a cutter frame (holder). The retaining plate comprises a plurality of bayonet form arms that make an advancing and retracting motion from the center toward the outside. The tip ends of these arms are engaged with and disengaged from the inside wall surface of the cutter frame. Furthermore, the shaving units are mounted on the retaining plate from the side and are elastically held in a mounted state by elastic arms that are integrally formed on the retaining plate, so that the shaving units move slightly upward and downward.
Japanese Utility Model Application Publication (Kokoku) No. H2-14748 discloses a shaver in which the outer circumferential edges of outer cutters are pressed by retaining body (20) that holds inner cutters, and this retaining body (20) is pressed against a cutter frame via a spring. More specifically, a locking body (50) is detachably mounted on the cutter frame, and this locking body (50) has a plurality of anchoring rods that protrude in the radial direction; and these anchoring rods are engaged with or disengaged from the cutter frame by turning the locking body (50). Furthermore, the retaining body is pressed by a single spring (57) mounted in the center of the locking body (50).
FIG. 8 is a top view showing the internal structure of another conventional example of a cutter frame, and FIG. 9 is a sectional view taken along the line 9—9 in FIG. 8.
In this conventional example, three outer cutters 1 are disposed in a common outer cutter holder 2 so that these outer cutters are positioned at the vertices of an equilateral triangle, and the respective outer cutters 1 are anchored to the outer cutter holder 2 so as to be depressable and tiltable. Three inner cutters 4 are held in a holder 3 so that these inner cutters are rotated in a depressable and tiltable manner. Two projections 5 protrude from this inner cutter holder 3 for each outer cutter 1, with these projections being separated in the circumferential direction of the outer cutters 1 so that the projections do not interfere with the outer cutter holder 2.
The center of the inner cutter holder 3 is elastically supported on the cutter frame 7 by a locking bolt 6. More specifically, a nut 8 is inserted into the center of the cutter frame 7, and the inner cutter holder 3 and compression coil spring 11 are disposed between a knob 10 and a retaining ring 9 anchored to the locking bolt 6. Here, the inner cutter holder 3 is pressed against the retaining ring 9 (i.e., toward the tip end of the locking bolt 6) by the coil spring 11. Accordingly, if the tip end of the locking bolt 6 is screwed into the nut 8, the inner cutter holder 3 presses against the outer cutters 1 in an elastic manner by means of the coil spring 11. In other words, the circumferential edges of the outer cutters 1 are pressed by the coil spring 11 via the inner cutter holder 3 that is integrated with the projections 5.
When the cutter frame 7 is mounted on the shaver main body (not shown in FIGS. 8 and 9), the inner cutters 4 engage with the drive shafts (not shown in 8 and 9) of the shaver main body and are rotationally driven. These drive shafts advance and retract in the axial direction with a return habit in the direction of protrusion and elastically press the inner cutters 4 against the inside surfaces of the outer cutters 1. Furthermore, three supporting protrusions 12 (only one is shown in FIG. 9) that support the outer cutter holder 2 in the vicinity of the vertices of the triangular shape are provided to protrude from the shaver main body.
In the shaver described in Japanese Patent No. 2853812, the movable range (range of vertical movement and tilting range) of the shaving units comprising outer cutters and inner cutters is limited to the movable range of the elastic arms that are integrated with the retaining plate and is therefore unavoidably extremely small. Accordingly, the outer cutters cannot sufficiently conform to indentations and projections or variations in the inclination of the shaving surface (skin), and the shaving characteristics are therefore poor. Furthermore, when shaving debris is cleaned away, the arms that protrude outward from the center (toward the inside wall of the cutter frame) are pressed toward the center with the fingertips, so that the tip ends of the arms are disengaged from the inside wall of the cutter frame; accordingly, a fine operation using the fingertips is required, and the operating characteristics are poor.
In the shaver described in Japanese Utility Model Application Publication (Kokoku) No. H2-14748, the retaining plate (20) that holds the inner cutters is elastically pressed toward the outer cutters. Accordingly, vertical movement of the outer cutters can be accomplished by vertical displacement of this retaining plate. However, in order to remove the retaining plate for the purpose of cleaning away shaving debris, it is necessary to turn the locking body (50) with the fingertips, thus making the operating characteristics poor.
In the conventional example shown in FIGS. 8 and 9, a nut 8 into which the tip end of the locking bolt 6 is screwed is inserted into the cutter frame 7, and this part is surrounded by the outer cutter holder 2. Accordingly, it becomes necessary to broaden the spacing of the outer cutters in the vicinity of this nut 8; and in cases where three outer cutters are used, it is necessary to broaden the spacing of the respective outer cutters or to increase the diameter of the respective outer cutters. As a result, the size of the cutter frame tends to increase. Likewise, in cases where two outer cutters are used, it is necessary to broaden the spacing of the outer cutters, and this has been a serious problem. Furthermore, when shaving debris is cleaned away, the locking bolt 6 must be rotated with the fingertips. The operating characteristics are thus poor.
Furthermore, in the shavers disclosed in FIGS. 8 and 9 and in Japanese Utility Model Application Publication (Kokoku) No. H2-14748, the retaining body (20) or inner cutter holder (3) is pressed by a single coil spring (57, 11) in the center. More specifically, the retaining body (20) or inner cutter holder (3) is elastically pressed by a coil spring (57, 11) mounted on the locking body (50) or locking bolt (6) fastened to the center of the cutter frame.
However, in a shaver in which the retaining body (20) or inner cutter holder (3) is thus pressed by a single coil spring (57, 11) in the center, the retaining body (20) or inner cutter holder (3) tends to move in the radial direction when the outer cutters are pressed downward. In the case of the shaver described in Japanese Utility Model Application Publication (Kokoku) No. H2-14748, the locking body (50) is firmly fastened to the cutter frame by means of a plurality of anchoring rods (52) that protrude in the radial direction. Accordingly, the retaining body (20) is aligned with the central shaft (protruding pin 15) which is fastened at both ends to the cutter frame and the locking body (50), and the movement of this retaining body (20) in the radial direction is restricted.
Meanwhile, in the shaver shown in FIGS. 8 and 9, the tip end of the locking bolt 6 is screwed into a nut 8 that is embedded in the cutter frame, so that a so-called cantilever support is constructed. Accordingly, the locking bolt 6 tends to be unstable, and the inner cutter holder 3 that is held here is also unstable. Accordingly, two pins 13 (see FIG. 8) protrude from the cutter frame 7, and these pins 13 are passed through the inner cutter holder 3.
In such cases, however, since there is only a single coil spring, it is necessary to use a coil spring with a strong spring force. Consequently, the detachment operating characteristics of the locking body (50) or locking bolt (6) when shaving debris is cleaned away are poor. Furthermore, the structure used to position the retaining body (20) or inner cutter holder (3) in the radial direction becomes complicated.